Armed with four patents, striking good looks and impressive functionality, the Classique Hora Mundi 5717 is sweet nourishment to time-starved frequent fliers

In the 1950s, when the world of the jetset was in its infancy, a brand new sort of timepiece was appearing on well-travelled wrists everywhere: the GMT or dual time wristwatch. The very first watch of this sort was even called a GMT watch and is now legendary – the Rolex GMT Master. This of course was just the beginning, for world travelers and for watchmakers alike.

The subject of GMT/ dual time watches, and all multi time zone (MTZ) watches in general, fascinates us to no end. From getting through security unmolested with a precious watch in tow to keeping track of time at home while traveling, we have previously explored these and other issues in general here and here. These stories serve as great introductions on the subject of MTZ watches.

In 2012, we have had the good fortune of getting a closer look at a couple of significant MTZ watches. We already brought you our review of the Calibre de Cartier Multiple Time Zone watch and our follow-up is this, the Breguet Classique Hora Mundi Ref. 5717. We find that both these watches challenge certain presumptions about MTZ propositions. For one thing, the typical large central hand showing time via a 24-hour scale is absent and, more importantly, the dials privilege clarity and legibility.

The trademark Breguet secret signature is on full display here. This and the numerals and hands make this a Breguet watch, through and through

To be sure, Ref. 5717 is a truly distinctive wristwatch, with a highly decorated dial and quite a classical overall aesthetic. Of course, the watch is part of Breguet’s Classique collection so this is to be expected. What you might not expect are the four patents that this watch boasts, given the classical spirit and such. This is not a La Tradition after all. Briefly, the Hora Mundi Ref. 5717 is the world’s first mechanical watch with instant jump time zones: all the displays change instantly at the push of a button. To put it another way, the watch delivers time in two of 24 times zones on demand.

Solid Gold

Looking closer at the dial, you will see a window at 6 o’clock that shows city names, thus hinting at what is going on here. As watch enthusiasts might guess, what is showing is part of a city disc, rather like that used by another sort of MTZ watch, the worldtimer. This also explains the bit about the 24 time zones as this is normal for worldtimers in general. We asked the Breguet representatives why the watch didn’t deliver half-time zones as well and they indicated that the brand did not want to seal the thunder of Blancpain, which has just such a complication (but not the on-demand functionality here).

Back to the business at hand, the highly legible dial makes space for an unusual dragging date display at 12 o’clock and a day/night indicator at 4 o’clock that looks for all the world like a moon phase indicator. Linger for more than a moment on the dial here because Breguet has lavished a wealth of decorative touches that you can show off to friends and acquaintances alike.

The pointer for the city indicator has a very high polish but there are so many details here, there isn't space in this caption to address them all. Pay special attention here to the waves

The generous 43mm case size also helps matters in terms of the display, giving the artisans plenty of real estate to show off their skills. Breguet does have a reputation for ornate - baroque even - styling and finishing and this is evident in Ref. 5717 too. Note the stylized representation of the world map comes in three versions. One shows Asia and the Pacific, another shows the Americas and finally, as seen here, Europe and Africa. Collectors who want Australia and India represented are advised to look for the Asia and Pacific version.

Note the deep blue of the lapis lazuli dial for the day/night indicator and the flecks of gold

In terms of technique, the artisans have utilized stamping and hand-engraving via a rose engine or engine turning lathe to create the textures on the solid gold dial, which is echoed in the border of the dial. You can best see the results in the texture of the waves in the center. The oceans are given multiple coats of lacquer, which contrasts nicely with the polish of the continents. From what we have seen of these sorts of techniques in the past, it takes the craftspeople however long it takes them and the attention to detail is much appreciated. For the day/date window, lapis lazuli (with pyrite inclusions for the stars) is used for the sky, with a hand-engraved disc of billowing clouds providing cover. The disc is made of silvered 18k gold. The sun and moon are made of solid gold – yellow gold for the sun and rhodium-plated yellow gold for the moon.

Patented Elegance

If nothing else, the dial shows one way in which a watch can apply the skills of artisans to get maximum impact without turning the entire watch into an attention-seeking bauble. For our part, we applaud this move and offer a salute to the classy elegance of ref. 5717. Now though, for the technical side of things, which is where the action really heats up, timekeeping-wise.

Once more, it is worth remembering that Ref. 5717 has four patents pending in relation to how it delivers time on-demand in two time zones. They are as follows, according to Breguet: a timepiece with two time zones mechanism; display of time zones on demand via only the main hour and minute hands; a programmable and reprogrammable mechanical memory wheel for a timepiece; and a mechanism for displaying an element of time by means of a dragging hand. We are not certain at this moment how a patent application could have been filed for a watch with two time zones given that such watches have existed since the 1930s (the worldtimer).

Take a moment to study the escapement, which is in silicon, like many newer movements from Breguet

There is not that much information available as to how the movement works but we will get to what we do know in a moment. Before we get into how it works, an explanation of what Ref. 5717 does: the watch does indeed keep track of time in two different time zones, as advertised. Once the initial setting of the watch is complete, the time zones can be switched with just the use of the combined crown/pusher at 8 o'clock. The key to making this all work seamlessly, and on demand, is accurate initial setting, much like the Cartier MTZ watch. A user simply selects two cities or time zones (Hong Kong for example reflects the standard time for China, Singapore, Malaysia and a host of other countries and regions) for the watch to display time for.

With this system, both time zones are effectively local time zones, instead of the usual home time and local time setting. First one sets time to one zone and then the next, with the aid of a stop-seconds function. Once set, the watch 'remembers' the time in both cities can toggle between them. Unlike most worldtimers, the watch cannot flip automatically to the other time zones, making this watch a proper two-time zone affair. Also unlike worldtimers and in fact any other MTZ watch, Ref. 5717 adds a swtich of date into the mix, with indication of day and night.

We see some interesting details on the bridge obscuring part of the barrel

In this shot, the crown/pusher at 8 o'clock looks much more like a pusher than a crown

Dragging It Out

Watching Ref. 5717 in action is quite a treat. The watch does not scrimp on visual effect and does not cheat, so to speak. If the second time zone to be shown is 14 hours ahead, for example, the hour hand makes the appropriate number of turns. Of course, all the indications change together, if so required. We suppose it pays to keep track of a time zone that requires as many turns to get to as possible.

With the functionality of Ref. 5717 out of the way, a few words about the movement. What we know is that the automatic calibre (in-house of course) 77F0 is built on calibre 777, with an additional module. The dragging hand indicates the date by following the correct numeral across the window at 12 o'clock, just as if the date disc below was dragging it. At the moment of date change, the hand jumps back to the new date. Apparently, the movement accomplishes this retrograde action via a rocker switch and two wheels fixed with reset levers and heart cams. Obviously, it also has some sort of mechanical memory system that allows Ref. 5717 to continue to keep track of times in two zones.

Even studying the movement up close does not reveal its secrets, at least to our untrained eyes. What can be seen that is interesting is the balance, which is in a most interesting shape, being free-sprung of course. The escapement - the balance spring and the Swiss in-line lever escapement - is in silicon, which has marked many a Breguet movement. This makes a nicely contemporary contrast with the finish, which is superb, of the same quality as the decorative touches on the dial. The final notes on the movement are in the specifications below.

The 18k gold oscillating weight is hand-engraved via the same rose engine that gives the dial's waves its special touch